Boom structure for wreckers and similar apparatus



y 5, 1953 E. w. HOLMES ETAL 2,637,447

BOOM STRUCTURE FOR WRECKERS AND SIMILAR APPARATUS Original Filed Dec. 28, 1944 '7 Sheets-Sheet l Qmvzmom E.W.HOLMES.

DECEASED 1 BY 55. STRANG ADMINISTRATO AND E.W. HOLMES,JR

BYMM

E. w. HOLMES ETAL 2,637,447

May 5, 1953 BOOM STRUCTURE FOR WRECKERS AND SIMILAR APPARATUS 7 Sheets-Sheet 2 Original Filed Dec. 28, 1944 ERNEST W. HOLMES, DECEASED May 5, 1953 E. W. HOLMES ET AL BOOM STRUCTURE FOR WRECKERS AND SIMILAR APPARATUS Original Filed Dec. 28, 1944 '7 Sheets-Sheet 3 A 10m M ATTORNEYS May 5, 1953 E. w. HOLMES ETAL BOOM STRUCTURE FOR WRECKERS AND SIMILAR APPARATUS Original Filed Dec. 28, 1944 7 Sheets-Sheet 4 :wmf LN I E.w. HOLMES, DECEASED BY s15. STRANG- ADMINISTRATOR AND E.VV. HOLMES, JR \LANA k/rm May 5, 1953 E. w. HOLMES ET AL 5 5 BOOM STRUCTURE FOR WRECKERS AND SIMILAR APPARATUS Original Filed Dec. 28, 1944 7 Sheets-Sheet 5 Z/ 1 5 31mm ERNEST w. HOLMES. DECEASED BY SAMUAL BmTow STRANQADMINISTRATOR AND ERNEST W.HOLMES J'R.

y 1953 E. w. HOLMES ET AL 2,637,447

BOOM STRUCTURE FOR WRECKERS AND SIMILAR APPARATUS Original Filed Dec. 28, 1944 7 Sheets-Sheet 6 I l I l I ERNEST W HOLMES, DECEASED BY- SAMUEL 'BARTOW STRANQADMINISTRATOR AND ERNEST W HOLMES, J'R.

May 5, 1953 E. w. HOLMES ET AL BOOM STRUCTURE FOR WREC'KERS AND SIMILAR APPARATUS Original Filed Dec. 28, 1944 '7 Sheets-Sheet '7 INVENTORS NEST W. HOLMES.

DECEASED BY SAMUEL B. STRANG ADMINISTRATOR AND ERNEST W HOLMES Patented May 5, 1953 BOOM STRUCTURE FOR WRECKERS AND SIMILAR APPARATUS Ernest W. Holmes, deceased, late of Chattanooga,

Tenn, by Samuel Bartow Strang, administrator, Chattanooga, 'lenn., and Ernest W. Holmes, Jin, Chattanooga, Tenn., assignors to Ernest Holmes (Company, a corporation of Tennessee Original application December 28, 1944, Serial No. 570,184, now Patent No. 2,479,009, dated August 16, 1949. Divided and this application June 14,

1949, Serial No. 99,093

9 Claims. (01. 212-55) The present invention relates to improvements in Wreckers and similar hoisting apparatus, and more especially apparatus of the mobile type adapted to be mounted on a truck or other suitable vehicle, and comprising means for handling disabled motor vehicles, and for performing hoisting, pulling, towing and other similar operations, this application being a division of application Ser. No. 570,184, filed December 28, 194-4, now Patent No. 2,479,009, granted August 16, 1949.

A primary object of the invention is to provide boom structure embodying a telescopic or extensible member which may be adjusted to increase or reduce the effective length of the boom, and thereby increase the range of operation of the boom.

Another object is to provide a boom having a member which may be extended to increase the effective length of the boom, or retracted to reduce the length of the boom under the control of power derived from. the wrecker.

Another object is to provide a telescopic or variable length boom having means whereby the operation of increasing the length of the boom auto matically raises the boom, and the operation of shortening the length of the boom automatically lowers it.

Another object is to provide a sheave at the top of the mast of the boom having a supporting bracket which is fixed to the mast to rotate therewith as the boom swings about its vertical axis, thereby effectively guiding the boom supporting cable and guiding this cable in directions to conform with the different angular positions into which the boom swings.

A further object of the invention is to provide a sheave at the lower end of the mast for guiding the boom supporting cable coaxially with the axis of rotation of the mast as this cable winds on and unwinds from its operating drum, thereby guiding this cable onto the drum during winding thereof and directing this cable into the mast during unwinding thereof from its drum.

To these and other ends, the invention consists in certain improvements and combinations and arrangements of parts, all as will be hereinafter more fully described, the features of novelty being pointed out more particularly in the claims at the end of this specification.

In the accompanying drawings:

Figure l is a side elevation of a wrecker constructed in accordance with the present invention.

Figure 2 is a rear elevation of the wrecker, showing the booms swung laterally from the respective sides thereof.

Figure 3 is an elevation, partly in vertical section, and on an enlarged scale, of the lower end of one of the booms and its mast.

Figure 4 isa top plan, partly in section, of portions of one side of the wrecker.

Figure 5 is a rear elevation of the structure shown in Fig.4.

Figure 6 is a top plan, partly in section, of the boom swinging mechanism at one side of the wrecker, showing also a portion of the driving means for the boom cable winding drum.

Figure '7 is a vertical section on the line 7-4 in Fig. 6.

Figure 8 is a detail section of the clutch for connecting the boom to the respective boom swinging mechanism.

Figure 9 is a detail sectional view of driving means for one of the service cable winding drums.

Figure 10 is a detail view of the friction drive for the service cable winding drum.

Figure 11 is a detail section through the winding drums for the service and boom supporting cables, showing the mountings for these drums and the worm drive for the boom supporting cable.

The invention as shown in the accompanying drawings is adapted to be mounted on the chassis of an automotive truck of suitable size and provided with an engine for propelling it, and having a power take-off, which may be of any suitable or well known type, for supplying power to operate various parts of the wrecker. Since the construction of the truck and its power take-off are well known, it is deemed sufficient to show only the longitudinal frame members I of the truck chassis on which the wrecker is mounted and suitably secured.

The wrecker comprises a frame, generall designated 2, composed of uprights at the respective sides of the frame, a pair of uprights at one side being designated 3. The upper ends of these uprights are rigidly connected by a cross member 4 composed preferably of a pair of channel irons secured together by top and bottom plates 5 and 3, and the lower ends of the uprights are rigidly secured to a supporting structure comprising preferably a channel iron I and an I-beam 8 rigidly secured together by top and bottom plates 9 and it, thus forming a base for the frame which extends outwardly from the adjacent sides of the longitudinal frame member I of the truck chassis.

The wrecker as shown is of the double boom type in which the booms IE and HSA are pivotally mounted at the respective sides of the frame to swing about vertical axes, these booms being each equipped with power means for swinging it laterally to different desired angles, means for raising and lowering the outer end thereof, and a service cable having means for winding and unwinding it to raise and lower the loads and to perform pulling and other operations, as will be hereinafter described.

Both booms and their associated parts are of the same construction, with the exception that they are mounted respectively on therlght-hand' and left-hand sides of the wrecker. Detail illustration and description of one of the booms and its associated parts will therefore sum'ce for both, the parts on the left-hand side being shown, and corresponding parts on the right-hand side being designated by the same reference numerals but with the distinguishing suffix A.

Each boom is supported at its inner end on a cap 16 to which it is pivotally connected for raising and lowering movements by a horizontal pivot pin H, the cap IE being bolted or otherwise fixed to the lower portion of a tubular mast it! the lower end of which is rotatable on a vertical axis in a bearing l9 supported by plate 9 attached to the base members 1 and 8 of the frame, as shown in Fig. 3., The upper end of the mast is rotatable in a bearing 20 which is supported by an extension of the plate 5 at the top of the frame.

A sheave bracket 21 is fixed to the upper end of the mast to rotate therewith, this bracket carrying sheaves 22 and 23 for the boom supporting cable 24, portions of this cable passing back and forth between the sheaves 23 and sheaves 25 rotatable in a yoke 26, and this yoke being connected to the outer end of the boom in any suitable manner, as for example, by the equalizing sling 21 and the sheaves 28 carried by the yoke 26, as shown and described fully in Patent No. 2,405,578, granted August 13, 1946. One end of the boom supporting cable 24 is attached by links 29 to the-yoke 26, and the other end of this cable around the sheave 22 and then down through the tubular mast to a drum for raising and lowering the boom, as will be hereinafter described. The outer end of the boom carries a sheave 80 around which the service or hoisting cable 3'] passes. this cablepassing through a guide 32 and usually extending downwardly from the outer end of the boom for hoisting and other operations. By fixing both the boom supporting cap l6 and the sheave bracket 2| to the mast, said bracketwill be rotated by the mast in unison and conformity with the lateral swinging movements of the boom about its vertical axis instead of depending. on the swing of the boom supportingv cable for rotating it.

The boom'and it's mast are rotatedlaterally into different positions about a vertical axis. by power means. The lower end of the mast l8 carries a gear wheel '35 which -is keyed :or otherwise fixed thereto, this gear being enclosed in a casing 36. A bracket -31, having a guide sheave '33 mounted therein, :is provided at the lower end of the mast, this bracket having a spindle531o which projects upwardly into the tubular mast, and a thrust shoulder 31b which bears :against the lower end of the mast, an angle iron bracket 31c being attached to the bracket '31 and to the :frame of the wrecker to hold-the bracket 31 from rotation when the mast is swung about its vertical axis. The boom cable 2 below the lower end of the mast passes around the sheave -38 and extends to the drum 39 onto and 'iromw'hich it is adapted to be wound and unwound by means hereinafter described. The "mast-swinging gear wheel is driven by a pinion lD iFigs. 6 and 7') which is fixed on a shaft 4!, the latter being journaled in a gear housing 42 and having a worm wheel 43 mounted for rotation thereon but is adapted to be coupled to the shaft 4| by a clutch collar it which is splined on said shaft and has jaws thereon to engage between complemental jaws on the, upper side of the worm wheel, the clutch collar being moved into engaged and disengaged relation with the worm wheel by a fork 45 which is fixed to a shaft 46 rotatable in the top of the housing 42, an end of this shaft extending to theexterior of the housing and having an oper ating arm fill fixed thereon, this arm being connected by the linkage shown to a rod 27"! connected to a controlling lever 215.

The worm wheel 43 is power driven by a worm 48. meshing therewith, this worm being fixed on a shaft ill journaled in the housing 42 by bearings. 53., the shaft 49 having a sprocket wheel 5| fixed thereon and driven by a chain 234 which is driven by a sprocket wheel 233 connected to a transmission 2 i E3, the shaft 2 i 2 of which is powerdriven by a sprocket wheel 213 fixed to this shaft and connected by a chain 2M to the power takeoff shaft 2H5 of the truck by a sprocket wheel 215. The detail construction of the transmission 21B is shown and described in the prior application hereinbefore referred to. A friction brake comprising a conical collar 52 splined on the shaft 49 by a key 53 and pressed irictionally against the adjacent end of the worm housing by a com pressed coil spring 54 prevents backing off of the worm wheel 43 while the power drive is not in operation. Rotation of the sprocket wheel 5! in one or the other direction will swing the boom from its normal position at the rear of the wrecker to or toward a position where it projects laterally therefrom, or vice versa. The clutch connection provided between the worm wheel 43 and pinion 4E] enables the boom swinging gear 35 and pinion 40 to be disconnected from the power drive for swinging the boom independently thereof, as manually by pulling the service cable laterally ofthe outer end of the boom.

According to the present invention, the boom is so constructed that it may be lengthened or shortened, as may be desired. Preferably and as shown in the present instance, each boom is composed of telescopic sections E and til, the section at the lower end or the boom having a bracket 62 fixed thereto to carry the horizontal pivot I1, and the other section 5| carrying the service cable sheave 38, and having the boom supporting sling 2! attached to its upper end. The section 6|, which slides within the section 6'3, has a lug 3 fixed thereon, this lug being slidable in a slot '64 extending longitudinally of the outer section 68 and having a cable attached thereto, this cable extending around a sheave 63 rotatable in a bracket 6! fixed on the outer section 69 and having a loop 58 or other attaching device on its free end. Engagement of the lug 33 in the slot 65 prevents rotation of the inner section within the outer section of the boom. By this arrangement a pull applied to the cable 65 will cause the inner boom section 6! to be pulled out or extended from the outer section 68. Such operation also serves to automatically swing the boom upwardly, since the boom cable 24 connected to the upper end of the boom section 6| acts as a radial tie of fixed length between the upper end of the section GI and the top of the mast, and as the length of the boom is increased by extending of the section 6|, the upper end of the boom is pelled to rise, and thus swing the boom upwardly. Such concurrent lengthening of the boom and swinging of the boom upwardly saves much time when it is desired to adjust the boom to reach relatively distant or high objects, or to lift objects to relatively high elevations. The boom section GI may be locked in different extended positions by inserting a locking pin 59 through diametrically opposite holes in the outer section 60 and through the appropriate pair of diametrically opposite holes H which re ister with the holes 10, a suitable number of pairs of holes 1I being spaced appropriately along the length of the boom section 6|. Return of the boom section BI to its normal position within the section 50 to shorten the boom'i accomplished by withdrawing the locking pin and allowing the cable 65 to return to its normal position. Pulling of the cable 65 to extend the boom, and controlling of the return of the boom to its normal length are preferably effected by unreeving the service cable 3I from the sheave 30 and guide 32 and attaching its hook to the loop 68 on the cable 55, and then operating the service cable by its winding and unwinding means.

Each service cable 3I extends down around a sheave 90 past an idler sheave 9| to a service drum 92. The sheave 90 is swivelled on the top of the cross member 4 of the frame, it being mounted rotatably on a shaft 93 (Fig. 4) which is fixed in the flanges 94 of a bracket 95. A vertically movable cable guide 91 is also provided for yieldingly supporting the service cable so that it will not foul the adjacent boom cable sheaves 22 and 23 as the service cable swings above said sheaves incident to the swing of the respective boom to and from a lateral position relatively to the wrecker. This cable guide 91 and the portion of the service cable resting thereon are yieldingly supported in elevated position by a coil spring 99 one end of which is hooked or connected to one of the guide arms 91 and the other end of the spring is connected to a sleeve fixed to the shaft 93 by a screw I02. The cable guide 91 serves to guide the service cable as it passes onto the sheave 90.

Each service cable is adapted to be wound upon and unwound from the drum 92 to perform the hoisting, pulling and other operations. This drum is mounted rotatably on a sleeve or hollow shaft I which spans the space between and is secured in a pair of plates I2I between which the drum is accommodated (Fig. 11), these plates being secured to the respective pair of uprights 3 (Fig. 4), their lower edges being bolted or otherwise secured firmly to the truck chassis on which the wrecker is mounted. Casing sections I22 and I23 are attached to the plates I2I to enclose the upper and lower sides of the service cable drum and its associated parts to protect them from the weather and for safety purposes.

The sleeve I20 also supports the boom cable drum 33 which is rotatably mounted thereon, this drum being driven by a plate I25 which is fixed thereto and to the outer end of a shaft I26 which is journaled in a bearing I21 supported within the sleeve I20, and said shaft is driven through a coupling I28 by power operating mechanism which will be hereinafter described.

Each service cable drum 92 is driven through a gear I30 which is formed integrally with or attached to one of its flanges. In the present instance, the service cable drum is driven by a two-speed drive to enable it to wind the service cable quickly while slack or under a light load,

and to be driven more slowly and with greater power while under a relatively heavy load, such two-speed drive being disclosed fully in the prior application hereinbefore referred to. For the purposes of the present invention, it is believed sufficient to describe this two-speed drive as comprising a main driving pinion I3I which meshes constantly with the gear I30, thi pinion being mounted rotatably on a shaft I33 journaled in bearings I34 and I35 fixed in the respective pair of plates I2I, this shaft being provided with splines I36 on which a clutch collar I31 is slidable, this clutch collar being thereby driven from said shaft and having clutch jaws I38 thereon which are engageable with or disengageable from complemental jaws on the adjacent side of the pinion I 3| whereby the latter may be coupled to and uncoupled from the shaft I33. The shaft I33 is provided at one end with a coupling I30 for connecting it to its power operating means, to be hereinafter described. A relatively large gear wheel I40 is fixed to the other end of the shaft I 33, and this gear wheel meshes with a relatively small pinion I4I mounted on a shaft I42, whereby the latter may be driven from the shaft I 33. A friction drive is preferably interposed between the shaft I42 and the pinion I4I whereby the drive of the shaft I42 will be relieved or interrupted automatically when the load on the service cable exceeds a given amount. For this purpose, the pinion MI is formed on or fixed to the hub of a friction drum I43 which is mounted rotatably on the shaft I42 and houses a pair of friction shoes I44 arranged to frictionally engage its interior surface under a pressure which is regulated by screws I45 which connect the shoes and are adjustable to relatively expand or contract the shoes. These shoes drive the shaft I42 through a cross arm I45 which is fixed to said shaft, the ends of this arm engaging in sockets I41 in the brake shoes. The shaft I42 has a gear I mounted rotatably thereon and adapted to be coupled thereto by a clutch collar I5! which is slidable on splines I52 on said shaft which splines drive said collar. The clutch collar I5I has clutch jaws I53 which are engageable with and disengageable from complemental clutch jaws provided on the adjacent face of the gear I5I. The gear I50 meshes with a gear I32 mounted on a shaft I54, this shaft and the shaft I42 being journaled in bearings mounted in the plates I2 I. Since the shaft I42 will be driven by the gear I40 and pinion MI in a direction reverse to the direction of rotation of th shaft I33, the pinion I32 is interposed as an idler gear between the gear I50 and the drum gear I30, so that the main pinion I 3| and also the higher speed or overdrive pinion I32 will both drive th drum in the same direction for a given direction of rotation of the drive shaft I33.

The main pinion I 3| and overdrive gear I53 are selectively rendered operative by a clutch shifter slide I50 slidable on a rail I6I parallel to the shafts I33 and I42 and carrying a shifter fork I62 which engages the clutch collar I31 and a similar shifter fork which engages the shifter collar I5I, so that While either of the clutch collars is engaged with its gear, the other clutch collar is disengaged from its gear, and while both clutch collars are disengaged, the drive for the service cable drum will be in neutral. The shifter slide is operated by a link I15 which may be operatively connected to a handle I13 by suitable means such as disclosed in detail in the prior application hereinbefore referred to.

' Each service cable drum 92 is driven from the main .Ltransmission am through a worm gearin 288 or 283A, the worm wheel shaft being connected to the respective coupling E39 and the worm being driven through appropriate gearing in the transmission, as fully shown and described in the prior application hereinoefore referred to, and each boom supporting cable drum 39 is driven through a worm gearing 3H1 or 3 MIA, shaft 3!? of each worm wheel 3!] being connected to the respective coupling i253 (Fig. 11) and the shaft 313 of the worm 3 I4 being connected by universal joints 315 and {HE and shaft 3!! to a sprocket wheel 3m mounted on a shaft 3|9 journaled in a bearing 328 bolted in fixed position on the base member I, the sprocket wheelv 3H5 being connected by a chain 321 to a sprocket wheel 26! on the main transmission 2H and driven by gearing as fully shown and described in the prior application hereinoefore referred to. The service cable drums are controlled by levers 2 55 and 254A connected to the appropriate control levers 243 on the transmission 2!!! by links 2.5L and the boom supporting cable drums are controlled'by levers 255 and 255A connected to the appropriate control levers 244 on the transmission by Links 2'52. Levers 253 and 253A control th power means for swinging the booms, they being connected to the appropriate control levers 242 on the transmission by links 251 A leg Mil is provided at each side oi the wrecker for stabilizing it when heavy loads are being lifted or pulled at a side, each leg comprising a tubular upper section 3M having lugs 332 pivotally connected to lugs 343 on the frame by a pin 3%, and a lower section M5 which telescopes within the section 341 and is provided with a foot 3&5 at its lower end for engagement with the ground. The lengthof the leg is adjusted according to the angle at which it is swung outwardly, and is locked at such length by a pin 3 which is inserted through holes in the upper section and appropriate holes 348 in the lower section.

In operation, when it is desired to raise either boom, as when a. relatively high object is to be lifted or an object is to be lifted to a relatively elevation, the appropriate control lever-255 or is operated to connect the respective boom cable winding drum to its power drive, and lifting or pulling of the load by the service cable is effected by operation of the appropriate control lever 25 or 356A which connects the corresponding, service cable winding drum to its power drive.

If the object to be lifted is at a greater distance than. usual. or is relatively high or is to be lifted to a relatively high position, the range of operation of th boom may be increased accordingly by lengthening the boom, such being accomplished by extending the inner section of the boom by pulling the cable 65, which may be done conveniently by unreeving the respective service cable from the sheave at the outer end of the boom and attaching it to the cable and then winding the service cable, which operation, as hereinbefore explained, not only extends the inner section or. the boom but also raises outer end. Return of the inner section of the boom to its normal position may also be controlled by the service cable,

We clain 1. In apparatus of the character described, the combination of a frame comprising upper and lower transverse members having bearings thereon, a, tubular mast piv-otally mounted at its, upper and lower ends in the hearings in the upper and lower-frame members respectively for rotation on a vertical axis, a boom attached to the lower portion of the mast adjacent to the bearing on the lower member or" the frame for rotation with the mast, a cable extending through the mast and over the upper transverse member of the frame and attached to the outer end of the boom for supporting it, and a bracket carrying a sheave for said cable fixed to the upper portion of the mast adjacent to the bearing on the upper member of the frame for rotation with the mast in accordance with swinging movements of the boom with the mast about its vertical axis, the sheave being mounted in said bracket in a position to guide said cabl for movement into and out of the upper end of said tubular mast.

' 2. Apparatus according to claim 1, including a lower sheave bracket bearing against the lower end of the mast and having a spindle thereonv which extends upwardly into and is rotatably engaged by th lower end of the mast, said lower sheave bracket carrying a sheave under which said cable passes, and means connected to said lower sheave bracket for holding it from rotation during rotation of the mas 3. A boom structure comprisi g a mast having means for mounting it in an upright position, a boom having means for pivotally connecting on end thereof to the lower portion of the mast to swing vertically and to swing laterally, said boom comprising a section which is e ztensible to vary the boom length, boom supporting means connected to the outer end of the boom extendillg over the upper portion of the mast, and means including a flexible member connected to said extensible section and extending toward the out or end of the boom and provided at its outer end with on attaching means for applying tension to said member to lengthen the boom, whereby lengthening of the boom will swing it upwardly and shortening of the boom will lower it.

4. A boom structure according to cl m 3, wherein said boom is composed of telescopic scc'- tions the outer of which is connected to the mast and the inner of which is connected to said boom supporting means, and including a sheave on the upper side of the outer section around which the outer end of flexible member 5. A boom structure according to claim 3, wherein said boom is composed of telescopic sections connected respectively to the mast and boom supporting means, the outer section having a slot extending longitudinally thereof, and including a flexible member having a lug thereon extending through said slot and connected to the inner section and extending toward the outer end of the boom-and having an attaching device at its outer end operable from the exterior of the outer section for extending the inner section.

6. A boom structure comprising a most, a boom composed of inner and outer telescopic sections, means pivotally connecting the inner end of one of said sections to the lower portion of the mast for raising and lowering movements of the boom, means conneced to the outer end of the other section and guided at the upper portion of the mast for supporting the outer end of the boom, the outer boom section having a slot extending longitudinally thereof and the inner section having a lug fixed thereto and movable ion itudinah ly in said slot in the outer section hen the sections are relatively extended, a sheave mount ed on the outer section adjacent/to the outer end of the slot therein, a cable connected to said lug and extending outwardly and around the sheave on the outer section, tension applying means connected to the outer end of said cable, and power means for operating said tension applying means to tension said cable to relatively extend the boom sections and thereby lengthen the boom, and means for retaining the boom sections in different relatively extended positions.

'7. In apparatus of the character described, the combination of an upright mast, a boom comprising an outer section pivotally connected to the lower portion of the mast and a longitudinally extensible inner section, th outer section having a longitudinally extending slot therein which exposes the inner section, a boom-supporting cable connected to the inner section of the boom and having means for guiding it over the top of the mast, a service cable having means for operating it, a sheave at the top of the mast over which the service cable extends, means including a flexible member connected to the inner section and extending toward the outer end of the boom and having at its outer end a tension applying device operable from the upper outer side of the outer boom section, and means for connecting the service cable to the tension applying device on said flexible member for applying tension thereto to extend said inner boom section and to thereby cause the boom supporting cable to swing the boom upwardly.

8. Apparatus as defined in claim '7, wherein said connecting means comprises a flexible cable connected to the inner boom section, a sheave mounted on the outer section of the boom remote 10 from its pivotal connection to the mast and around which the outer end of said flexible cable extends, and means for connecting the outer end of said flexible cable to the service cable.

9. Apparatus as defined in claim 7, wherein the boom comprises telescopic sections the outer one of which is provided with a longitudinal slot in its upper wall and with holes in its side walls and the inner section of which is provided with a lug for connecting said flexible member thereto and arranged to travel in said slot in the outer section and having a series of longitudinally spaced holes the side walls thereof arranged to register with the first-mentioned holes in the outer section, and a pin insertable selectively in holes in said sections to lock them in one or another relatively extended relation.

S. BARTOW STRANG, Administrator of the estate of Ernest W. Holmes,

deceased.

ERNEST W. HOLMES, JR.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 889,054 Smith et a1 May 26, 1903 965,741 Peters July 26, 1910 984,670 I-Ieedwell et a1 Feb. 21, 1911 1,345,304 Zied June 29, 1920 1,917,053 Nelson et ai. July 4, 1933 

